More than half a century ago, a renowned biologist concluded that wild rice doesn't grow well in lakes that are high in a type of mineral salt that comes pouring off Minnesota's Iron Range.

Now, after three years of lawsuits, legislative wrangling and one of the most comprehensive scientific investigations ever conducted on behalf of a single species, it turns out he was right.

This week, in a decision with far-reaching implications for the state's mining industry and the preservation of its most famous plant, state pollution officials are expected to announce their recommendation for a "sulfate standard" — how much of that salt Minnesota industries can discharge into the clear, calm waters across the state where wild rice likes to grow.

If scientific findings are the guide, which has been the one unifying principal among all the opposing interests, then hundreds of mines, wastewater treatment plants and other facilities may have to come up with new and expensive ways to reduce a pollutant that was long regarded as fairly benign.

"There will be a lot of screaming about this, I'm sure," said Nancy Schuldt, a water quality expert with the Fond du Lac Band of Lake Superior Chippewa, which has pushed the state for years to enforce its long-standing rule to protect wild rice from the mineral salt called sulfate.

Craig Pagel, president of the Iron Mining Association of Minnesota, said the industry cannot estimate the costs of complying, but said: "I'm sure it would be extremely costly. And not just for us."

It's also clear, now, that it's not just wild rice that suffers from too much sulfate. The toxic reaction that occurs in the muck around the plant's roots can affect virtually all types of aquatic flora, or any type of living thing that relies on oxygen, scientists say.

"It's going to affect everything out there," said John Pastor, a biologist at the University of Minnesota Duluth, who ran one of the wild rice studies. "It's going to affect the whole food web."

The decision next week by the Minnesota Pollution Control Agency (MPCA) will pertain only to wild rice, however, and will mark a turning point in what has been an unusually contentious debate.

The MPCA will recommend whether the state's existing standard should remain where it is, or go up or down, or even vary by season. Next, the standard is likely to be reviewed by a scientific panel convened by the agency, according to Shannon Lotthammer, an MPCA director — a step that industry groups said they applaud. The public will have a chance to weigh in as well. A final decision will probably be made by the end of the year, she said.

That may be just the beginning. The rule will apply to waters where wild rice grows — or has grown, or could grow. In the land of 10,000 lakes, where wild rice used to be ubiquitous, determining the reach of the new standard is in many ways a far more complicated question than the chemistry.

A second process will determine which and how many lakes, rivers and wetlands will be defined, and then protected, as a wild rice water.

"And that," said Schuldt, "Is where the biggest battles over implementing this rule will fall."

Pioneering science

In the 1930s and 1940s, state biologist John Moyle paddled through lakes and rivers across Minnesota, studying the relationships between naturally occurring stands of wild rice and the concentration of sulfate. The plant grows best in shallow, mucky water with a gentle flow, and it was once common throughout the marshy areas of Minnesota, Wisconsin, Michigan, Ontario and beyond.

Indian tribes say that historically it was instrumental in their settlement around the region, and remains a foundation of their diet, culture and spirituality.

Today most of the wild rice grows in northeast Minnesota.

Naturally occurring sulfate is not common in the region. In northeast Minnesota, the primary source of sulfate is what leaches off piles of waste rock and tailings ponds from a century of iron and taconite mining on the Range.

Other industries, including wastewater treatment plants, contribute as well.

Moyle found that wild rice was sparse anywhere the sulfate concentration was 10 parts per million or higher. In 1973, in recognition of the grain's cultural importance to the state, Minnesota adopted that as a standard specifically to protect waters that produce wild rice.

In a significant catch, however, with only one exception, the standard was never enforced, said Lotthammer ­— in part because no one was sure what a wild rice water actually was. "That's what comes up every time," she said.

Fast forward to the 21st century. The MPCA, partly because of questions raised by the Indian tribes and the U.S. Environmental Protection Agency (EPA), began to rethink its enforcement of the rule, and in 2010 decided to review it.

Industry groups, including the Minnesota Chamber of Commerce, were angered that the state was suddenly going to enforce the rule, and challenged Moyle's science.

They said enforcing the standard could cost businesses and consumers millions of dollars and put the taconite industry at risk, as well as bringing a halt to the potential for a new copper mining industry. The chamber filed suit, but lost.

The Legislature tried to create a new standard, but the EPA overruled it, saying legislators couldn't write a standard without the science to back it up.

Now, thanks to $1.5 million in state funding, the science is done. "We have, more or less, known that Moyle was correct," Pastor said. "What we now know is why he was correct."

Seedlings at risk

Sulfate by itself does not hurt wild rice. But when it gets down into the mud, microbes eat it and then it converts to hydrogen sulfide — that rotten egg smell familiar to anyone who's found themselves tromping through a wetland. And sulfide is toxic.

"If conditions are right, it doesn't take much … to have a serious mortality on seedlings," said Pastor, who tested wild rice grown with different concentrations of sulfate in dozens of stock tanks.

Researchers also now understand what was always a puzzler — why wild rice sometimes appears to grow just fine in water that is high in sulfate.

It turns out that when water also contains dissolved iron, a chemical reaction renders the sulfide harmless.

The same processes affect all other aquatic plants except cattails, said Dan Engstrom, a research scientist with the St. Croix Watershed Research Station, who reviewed the results of tests conducted at 120 wild rice sites across the state.

"Wild rice may be the plant we worry about," he said. "But it's the whole ecosystem."

Now, it's up to regulators at the MPCA to figure out how to use that science.

"They've done a nice job," said Tony Kwilas, director of environmental policy for the Minnesota Chamber of Commerce. "It's an important issue to our members, and we look forward to working with the agency."

It is equally important to the Indian tribes and others who want to see those graceful stands of wild rice remain a common site across the landscape.

"And this is why the ecology should prevail, and not the politics," said Schuldt.

Josephine Marcotty • 612-673-7394